Powerchip offers a reprogramming of the E39 M5's engine management system that eliminates the top speed limit, raises the rpm limit, and increases horsepower from 394 to 405, and torque from 368 to 379, requiring only that the owner use 93 octane or better gasoline. The greatest torque improvement occurs in the low and mid range, where it would be of greatest benefit for day-to-day driving.
Has anyone used the Powerchip reprogramming, or dyno'ed the car afterward? Is the benefit worth the cost? Any negatives?